The Valle de Bravo Volcanic Field. A monogenetic field in the central front of the Mexican Volcanic Belt

HR: 0830h
AN: V51G-0361 [PDF]
TI: The Valle de Bravo Volcanic Field. A monogenetic field in the central front of the Mexican Volcanic Belt
AU: * Aguirre-Diaz, G J
AF: Centro de Geociencias, UNAM, Campus Juriquilla, Queretaro, Qro 76230 Mexico
AU: Jaimes-Viera, M d
EM: cjaimes@geociencias.unam.mx
AF: Centro de Geociencias, UNAM, Campus Juriquilla, Queretaro, Qro 76230 Mexico
AU: Nieto-Obreg▋, J
EM: nieto@servidor.unam.mx
AF: Facultad de Ingenieria, UNAM, Ciudad Universitaria, Mexico, DF 04510 Mexico
AU: Lozano-Santacruz, R
EM: rufino@servidor.unam.mx
AF: Instituto de Geologia, UNAM, Ciudad Universitaria, Mexico, DF 04510 Mexico
AB: The Valle de Bravo volcanic field, VBVF, is located in the central-southern front of the Mexican Volcanic Belt just to the southwest of Nevado de Toluca volcano. The VBVF covers 3,703 square Km and includes at least 122 cinder cones, 1 shield volcano, several domes, and the 2 volcanic complexes of Zitacuaro and Villa de Allende. Morphometric parameters calibrated with isotopic ages of the volcanic products indicate four groups or units for the VBVF, Pliocene domes and lava flows, undifferentiated Pleistocene lava flows,$>$ 40 Ka cones and lavas, 40 to 25 Ka cones and lavas, 25 to 10 Ka cones and lavas, and $<$ 10 Ka cones and lavas. Whole-rock chemistry shows that all products of the VBVF range from basaltic andesites to dacites. No basalts were found, in spite of many units are olivine-rich and large some with large weight percent contents of MgO, 1 to 9. There is the possibility that some or all of the olivines in some samples could be xenocrysts. Some andesites are high in Sr, 1000 to 1800 ppm, that correlates with relatively high values of Ba, Cr, Ni, Cu, CaO and MgO. Y and Nb have the typical low values for orogenic rocks. The only shield volcano of the VBVF has a base of 9 Km, and its composition is practically the average composition of the whole field. Stratigraphycally, it is one of the earlier events of the VBVF. Compared with other volcanic fields of the Mexican Volcanic Belt, it lacks basalts and alkalic rocks. All volcanism of this field is calcalkaline
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting